1. Field of the Invention
The invention relates to medical or surgical tubing, and medical/surgical devices which include such tubing. The invention also relates to a method and apparatus for forming medical/surgical tubing and devices which include medical/surgical tubing. More particularly, the invention relates to medical/surgical tubing and associated devices, in which a portion of the tubing is reinforced and another portion of the tubing is not reinforced.
2. Background of the Invention
Medical/surgical tubing is utilized in a number of devices. For example, in a tracheal tube, the tubing provides an air or oxygen passageway into the patient. Medical/surgical tubing is also utilized in other devices, such as catheter devices, in which the catheter provides a passageway into the body for fluids and/or surgical tools or utensils.
The tubing utilized in devices such as a tracheal tube is preferably flexible so that tissue abrasion or discomfort to the patient is minimized, and so that the tubing can be fed through curved passageways. However, the tube must also be able to resist collapse so that the passageway provided by the tubing is unobstructed even if the tubing is bent. One presently preferred tubing which accomplishes these objectives is a polyurethane tubing which is reinforced with a helical wire coil. When reinforced tubing is utilized in a tracheal tube, it is preferable to provide an end portion of the tube which is not reinforced, to provide greater comfort to the patient and avoid tissue damage, particularly when the tracheal tube is being inserted. The unreinforced portion is particularly important with tracheal tubes since throat tissues are very delicate. However, the provision of an unreinforced portion can also be desirable in other devices, such as catheter devices.
Reinforced tubing can be provided with an unreinforced portion by adding an unreinforced tube portion onto the end of the reinforced tubing, so that the tracheal tube (or other device) is reinforced over most of its length, while an unreinforced end portion is provided at the end which is initially inserted into the patient. However, this arrangement is undesirable in that there is a risk that the added unreinforced portion could become loose and lodged within the patient. In addition, even with the added unreinforced portion, the end of the reinforcing helical coil can protrude through the tube wall and cause discomfort and/or tissue abrasion.
U.S. Pat. No. 4,990,143 to Sheridan discloses prior art double-walled reinforced medical/surgical tubing in which the wire reinforcing element is disposed between inner and outer tube walls. Sheridan also discloses that an unreinforced portion can be provided by a number of methods including: (1) fusing an unreinforced tip onto the reinforced tubing, (2) extruding an unreinforced tip onto the tubing, (3) stripping the wire from between the tube walls, thereafter welding the walls together with glue, heat molding the end, and eye punching the tubing, and (4) intermittently stopping the feed of the wire during production of the tubing. Sheridan also discloses that, with prior art arrangements, in order to prevent protrusion of the wire end through the wall of the tube, a small loop can be formed in the end of the wire. Recognizing the shortcomings of such approaches, Sheridan avoids the use of a wire reinforcing element in favor of a non-metal filament which extends along the entire length of the tube. After the tube is cut, additional plastic may be added to the end of the tube, or the tube can be melted to finish the end of the tube (with the filament apparently melting with the tube so that a smooth end is provided).
The Sheridan approach either requires the addition of plastic at the end of the tube section or, if a plastic end is not added, the filament extends along the entire length of the tube, so that the same amount of reinforcement is provided along the entire length of the tube. The Sheridan approach is disadvantageous in that a compromise must be made in attempting to provide sufficient strength of the tube while also attempting to provide comfort and avoid abrasion caused by the distal end of the tube. Arrangements disclosed in Sheridan can also be disadvantageous in that they utilize multiple tube walls, with the reinforcing element or filament disposed between the tube walls. Multiple tube arrangements can be undesirable in that, for a given inside diameter, a larger outside diameter of the tubing results. However, it is preferable to minimize the outside diameter of a tube for a given inside diameter, in order to minimize the discomfort to the patient and the potential for tissue damage.